Performance of point-of-care tests for diagnosing feline immunodeficiency virus infection in captive African lions (Panthera leo).

Point-of-care (PoC) antibody (Ab) testing forms an integral component of feline immunodeficiency virus (FIV) diagnosis in both domestic and non-domestic felids, with test kits designed for use in domestic cats frequently extrapolated for use in their wild counterparts. The SNAP® FIV/FeLV Combo lateral flow ELISA is commonly used to assign FIV infection status in wild and captive African lions (Panthera leo). The aim of this study was to investigate the performance of four other commercially available PoC FIV antibody test kits in African lions held in Australian zoos, when compared to SNAP® as a quasi-reference test. To first validate the use of SNAP®, a subset of samples from SNAP® FIV-positive (n = 3) and SNAP® FIV-negative (n = 23) lions were evaluated with Western blotting, with perfect agreement demonstrated (Cohen's kappa coefficient = 1). Forty-eight serum samples from SNAP® FIV-positive (n = 16) and SNAP® FIV-negative (n = 32) lions were then assessed with Anigen Rapid®, Witness®, VetScan® Rapid and SensPERT® FIV Ab tests. No seropositivity was observed in FIV-infected lion sera using Anigen Rapid® or Witness® (Se 0%, Sp 100%), which utilise domestic cat FIV (FIV-Fca) transmembrane glycoprotein gp40 as their capture antigen. In contrast, VetScan® Rapid, which employs FIV-Fca capsid protein p24 as its capture antigen, demonstrated excellent performance (Se 100%, Sp 96.9%). The presence of p24 as a capture antigen did not guarantee the performance of an assay, as SensPERT®, which also features p24 as its capture antigen, was significantly less sensitive than VetScan® Rapid (Se 25%, Sp 100%; p < 0.001). Our findings have important implications for captive threatened felids, where timely, accurate diagnosis and careful management are critical for minimising retroviral transmission. We recommend using SNAP® or VetScan® Rapid FIV Ab tests for accurate diagnosis of FIV infection in African lions; however, the original VetScan® Rapid FIV test has been unavailable in Australia since 2019.